Holder was shot in the throat July 23 when he
opened fire on police officers as they tried to arrest him, wounding one of them in the groin.

The teenage suspect had survived his injuries and now faces charges of capital murder and attempted capital murder in connection to the shooting of a police officer.

Holder remains in jail on $1million bail and is due back in court Thursday.

According to a report recently released by the Tarrant County Medical Examiner's Office, Alanna's official cause of death determined to be was asphyxiation from the four plastic shopping bags wrapped around her head.

New documents made public in the case and cited byDallas Morning News show that police believe Holder acted alone, but may have used his mother's car to abduct the child and then dispose of her body.

The documents also state that Holder bought a new cell phone two days after Alanna's murder.

The teen gave his old phone to a friend, who told police after Holder’s arrest July 23 that he had discovered a YouTube search for 'Good kid porn websites' on the device, as well as images of male genitals and pictures of the suspect dressed as a woman.

Brutal death: Alanna's official cause of death has been determined to be asphyxiation from plastic shopping bags placed over her head

Anti-social: Holder, who has been described as a trouble-maker, lived opposite Alanna in Saginaw. A street view picture of his home shows two people making obscene gestures at the Google camera

The 17-year-old accused of brutally
raping and murdering his 6-year-old neighbor left a note for his mother
that read: 'I love you, I'm sorry,' according to FBI documents.

Duct
tape, used condoms and blood-stained toilet paper were also listed as
items found by officers when they searched Tyler Holder's home.

However, the first item listed on a receipt of 153 items seized by the FBI, according to KHOU, was a 'sealed letter addressed to Mom with 'I
love you, I'm sorry', and a crumpled up piece of paper with the
words 'Mom I' on it.

Holder's
neighbors had described him as a trouble maker who had been involved in
'criminal mischief', the arrest warrant showed.

Classmates
have also described the 17-year-old as 'socially awkward' and in a
Google picture of the suspect's home, two obscured people can be seen
making obscene hand gestures at the Google car camera. It has not been
confirmed if Holder was in the picture.

According
to the warrant, Alanna was sexually assaulted and suffocated, before
her wrists and ankles were bound with red duct tape, and her body was
dumped in a tarp less than a mile from her home July 1.

When investigators later searched Holder's home, they discovered a
purple Timex watch with pink and green flowers on it, which matched the description of the timepiece Alanna's parents had given her so the girl would know when to come home while playing outside.

Girls' necklaces
and jewelry, latex gloves, computers, digital
cameras and a journal were also seized.

'The three of us': A Facebook image shows Alanna's parents, Laura
and Karl (left) Gallagher with Miles McDaniel (right), who are in a
polyamorous relationship

Boyfriend: Patricia Hustede banned Holder from her home after he started dating her daughter, Cassie

Officers were able to trace a roll of toilet paper found with Alanna's body to Costco, which Holder's mother was a member of.

Originally, Saginaw Police had said
they had no specific suspects, but the affidavit suggests Holder was
under suspicion almost immediately, according to8 News.

Within
hours of Alanna’s body being found, officers reported seeing Tyler
Holder 'pacing up and down the sidewalk', the affidavit says.

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Residents
informed police Holder had told them it was Alanna’s body that had
been found, even before the authorities had revealed the identity of
the victim.

The next day, as officers searched the Gallagher home, Holder was seen standing across the street watching.

Holder
was questioned early in the investigation and told police on the day of
Alanna's death he woke up about 2pm, watched television and went to
apply for jobs, having recently been made unemployed by Sonic.

The affidavit reads: 'Holder stated that he had no contact with Alanna Gallagher and that she had never been in his house,'

Holder also denied having a tarpaulin in his back garden.

Weapons: Holder was said to have carried knives and pulled one on a teenage boy after destroying his snowman, according to one source

Tragic: Six-year-old Alanna Gallagher was found
bound and gagged. The youngster had been raped. Right, Charles Lodotto,
who Holder allegedly opened fire, on hitting the officer in the groin

But
video surveillance obtained from the north and south ends of Babbling
Brook Drive did not show Holder driving his vehicle that day as he had
said.

When they analyzed his mobile phone, they found pictures of him with a garden hose in a sexual position.

During an interview, Holder had admitted that he had sex with other men.

Belt: A DNA sample taken by police of Holder matched DNA found on Alanna's body and on a belt found at the scene

On July 5, officers took a DNA sample from his mouth and were later notified that it matched evidence found on Alanna's body.

Four days later, officers arrived at
Holder's home in unmarked cars. Neighbors heard them pounding on the
door shortly before multiple shots rang out.

Charles Lodatto, an officer who was
wounded during the confrontation, was shot in the groin and the bullet
hit an artery and broke into pieces.

The
probable cause affidavit for Holder’s arrest offered gruesome details about the suffering inflicted upon
Alanna, who went missing July 1.

The little girl, who was known for riding on her purple scooter in search of playmates, had been brutally raped.

Her partially clothed body was found by 14-year-old Owen
Whiddon bound and wrapped in a
gray tarpaulin in the middle of a street about a mile from her home
later in the day of her disappearance.

Genetic
evidence was matched through DNA tests to a sample that Holder
voluntarily provided to police earlier this month, the documents say.

His DNA was also found on the buckle of a belt used to wrap Alanna’s body in the tarp.

Four Walmart bags were taped over the girl’s head with red duct tape secured around her neck.

Scene: Five officers arrived at the home in Saginaw, Texas and allegedly watched as Holder pulled out a gun from his wasitband. He is said to have shot one officer, hitting him in the groin, before he was shot in the head

Heartbreaking: The arrest comes after Alanna's body was found tied and partially naked with a bag over her head under this tarp in the street. A 14-year-old boy found her body

Her wrists and ankles were bound with the same tape and her body and clothes were wet with an unknown liquid.

Police
later found what is believed to be the same kind of duct tape in
rubbish bags outside the home Holder shared with his mother just two
doors from where Alanna lived with her family.

Alanna lived with her siblings, their
parents Laura and Karl Gallagher, and a second male, Miles McDaniel, who
was in a polyamorous relationship with her parents.

Police
have said that the Gallaghers and McDaniel were home while Alanna
played outside alone. They are not sure when she was abducted from the
neighborhood.

Coping: Neighbors set up a makeshift
memorial on the curb but it was torched along with the
family's car